build/debian: Build and use our custom Debian kernel

In this CL, we introduce a new flag `-k` to allow building our own Debian kernel (as opposed to using the default cloud kernel) in our FAI workflow.

- Add a new `avf` kernel flavour based on the existing `cloud` flavour
- Build `avf-amd64` (or `avf-arm64`) headers and image, and generate `.deb` packages
- Copy `.deb` packages to FAI's `localdebs` location and add package names to `package_config/AVF` for FAI to pick up during installation

Bug: 380176863
Change-Id: Ic3737746ff8b8949173fea79a6b6d0173fda058c
Test: ./build_in_container.sh -k
Test: ./build_in_container.sh -a aarch64 -k
diff --git a/build/debian/build_in_container.sh b/build/debian/build_in_container.sh
index 5028b74..967f5ab 100755
--- a/build/debian/build_in_container.sh
+++ b/build/debian/build_in_container.sh
@@ -6,17 +6,19 @@
   echo "Options:"
   echo "-h         Print usage and this help message and exit."
   echo "-a ARCH    Architecture of the image [default is host arch: $(uname -m)]"
+  echo "-k         Build and use our custom kernel [default is cloud kernel]"
   echo "-r         Release mode build"
   echo "-s         Leave a shell open [default: only if the build fails]"
   echo "-w         Save temp work directory in the container [for debugging]"
 }
 
 arch="$(uname -m)"
+kernel_flag=
 release_flag=
 save_workdir_flag=
 shell_condition="||"
 
-while getopts "a:rsw" option; do
+while getopts "a:hkrsw" option; do
   case ${option} in
     a)
       arch="$OPTARG"
@@ -24,6 +26,9 @@
     h)
       show_help ; exit
       ;;
+    k)
+      kernel_flag="-k"
+      ;;
     r)
       release_flag="-r"
       ;;
@@ -53,4 +58,4 @@
   -v "$ANDROID_BUILD_TOP/packages/modules/Virtualization:/root/Virtualization" \
   --workdir /root/Virtualization/build/debian \
   ubuntu:22.04 \
-  bash -c "/root/Virtualization/build/debian/build.sh -a $arch $release_flag $save_workdir_flag $shell_condition bash"
+  bash -c "/root/Virtualization/build/debian/build.sh -a $arch $release_flag $kernel_flag $save_workdir_flag $shell_condition bash"